This invention relates generally to an endoprosthetic device which allows for total replacement of the metatarso-phalangeal joint of a human being, and specifically, to a replacement joint which most closely imitates the human metatarso-phalangeal joint. The device is implanted in the hollowed out intramedullary space in the bone ends.
A search of the prior art shows a dearth of replacement devices for the human metatarso-phalangeal joint, and those which do exist, have several deficiencies, the primary deficiency being that, once implanted, are deleteriously affected by certain stresses placed upon the foot. Another deficiency is that prior art devices do not provide for total joint movement that closely assimulates an actual human joint. The actual human joint is constructed by nature to provide motion in three planes about the joint, which includes dorsi flexion of 90 degrees, a plantar flexion of from 45 to 60 degrees, medial deviation from 1 to 5 degrees, and lateral deviation from 1 to 5 degrees, while at the same time directly bearing weight. The prior art deficiencies have resulted in fracture of the stem, fracture of the hinge, and rotation of the joint in the intramedullary canal. These deficiencies greatly restrict a patient's movement and activities, preventing the patient from returning to a normal state.
The present invention overcomes deficiencies found in the prior art by providing an artificial metatarso-phalangeal joint which may be used to replace the human joint and which provides for a weight bearing joint which is essential for the proper motion of the person in conjunction with a sturdy and reliable joint that is capable of duplicating the motion and withstanding the forces encountered as in a normal human metatarso-phalangeal joint.